On the western edge of Black Forest, deep into the mountains where miners once quarried for silver, lies Germany’s cultural heritage. It’s housed inside an old tunnel driven into the rocks for nearly 700 meters whose entrance is now barred by a heavy steel door. Behind this door are hundreds of stainless steel barrels stacked waist-high. Inside these hermetically sealed barrels are copies of the country's most important cultural documents and images etched in microfilm. Safely buried under 400 meters of granite and gneiss, these canisters and the precious film they contain are expected to survive for at least 500 years through any natural disaster and nuclear attack.

The entrance to the Barbarastollen underground archive.

The Barbarastollen underground archive is located near the village of Oberried, in Breisgau. The tunnel itself was built in 1903 originally to transport material and ore from the mines to a train station planned in Hintertal. But after carving for 700 meters, work was abandoned. It was repurposed as an underground archive during the early 1970s.

The Barbarastollen underground archive is one of only five such sites worldwide created under the “Hague Convention for the Protection of Cultural Property in the Event of Armed Conflict”. The need to protect one’s cultural property was realized after the world witnessed the wide scale destruction of art and books in the hands of the Nazis during the Second World War. Deeply shocked by the senseless destruction, Germany, along with more than one hundred and thirty other countries, signed the Hague Convention in 1954. Never again, the parties agreed, would inheritance become the victims of war, as “any damage to cultural property, irrespective of the people it belongs to, is a damage to the cultural heritage of all humanity, because every people contributes to the world's culture,” the preamble of the treaty reads.

As the nuclear threat loomed large during the Cold War, Germany decided to act. Barbarastollen was chosen as the site where the archive would be created. Remotely located, the place was far from military bases, airports, major stations and anything of importance that could draw enemy attack. Besides, it already had a well bore tunnel through rocks hard enough to withstand earthquake, meteorite strikes and nuclear explosions.

Access to the storage tunnels, just after the entrance to the tunnel. From 1972 to 1974 the tunnels were gradually converted, and the first barrels of microfilm arrived in 1975. At that time electronic media such as hard drives and optical drives did not exist, and these media also have very limited shelf life and therefore unsuitable. Microfilm, in comparison, has a lifetime of 500 to 1,500 years if properly stored. Consequently, the tunnels are kept at a constant 10 degrees and the containers are sealed at 35 percent humidity.

Besides, digital storage media need specialized equipment to make them readable, and this technology is rapidly changing. If stored in digital medium, the data would have to be constantly updated to current technology. To read a microfilm, on the other hand, one only needs sunlight and a magnifying glass.

Over 44,000 kilometers of microfilm containing more than one billion images and an equal number of documents are stored at Barbarastollen inside 2,000 barrels. The oldest document dates back to the sixth century. The most recent is the schedule of the Bayreuth Music Festival in 1989. Between these are millions of images, manuscripts and documents ranging from the coronation certificate of Otto the Great from 936 and the Peace of Westphalia signed in 1648, to the construction plans of Cologne Cathedral and the certificate of appointment of Adolf Hitler as German Chancellor. There are manuscripts of Goethe, Schiller, Kafka, scores of Bach Bismarck's social laws, and archival material from the GDR.

Barrel No. 2165 containing the one billionth document—a facsimile of the constitution of the Federal Republic of Germany—displayed at Barbarastollen in 2016 when it was formally added to the archive. The actual constitution along with a sample of archive film and a magnifier is displayed alongside.

Barbarastollen is one of the most protected places in Germany, but in a strange way. No military vehicle is allowed to come within three kilometers of the property and the terrain is a strictly no-fly zone. The code to open the steel door is known to only two men from the security service.

The importance of the place can be identified by the emblem at its entrance depicting three downwards pointed shields in ultramarine blue and white. Only the Vatican and the Rijksmuseum in Amsterdam wear these emblems signifying the highest level of protection from the United Nations.

Even without nuclear attack the tunnel has already proved to be useful. In 2009, the building of Cologne's Historical Archives collapsed and nearly 90 percent of the archives was lost. The remaining, amounting to around 1 million photographs, was brought to Barbarastollen. Records continue to be added to the archive at the rate of 1.5 million documents per year.